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Last modified Mon Sep 26 23:04:13 EDT 2005
There is no super-user; the closest equivalent is the person who booted the terminal (generically called Eve; Adm owns the file server). Most devices are owned by Eve, and the local kernel will let Eve do most things commonly associated with a super-user (for example, debug or kill processes she doesn't own). Eve's power does not extend past the local machine, though, or even into the kfs file system. The important difference is that the kfs file system is being provided by a user process, which has its own permissions checking separate from the kernel, and it does not care to let the hostowner have special permissions directly.
Of course, permissions need to be bypassed once in a while. For example, the file /adm/users (the equivalent of a combination of Unix's /etc/passwd and /etc/group) is not writable except by members of group adm. Rather than put yourself into the group adm, we usually type 'disk/kfscmd allow' to turn off permission checking on the kfs file server, edit /adm/users, make kfs read it back by typing disk/kfscmd user, and then turn permission checking back on by typing 'disk/kfscmd disallow' (If you're running a network file server, the preferred but rarer setup, all this hair-raising stuff is avoided; appropriate control is provided on the file server console and nowhere else.)
To add a new user, add the user to the /adm/users file and then run the user command; the format of the file is documented in users(6). (Note that on a standalone file server, the newuser command manages users, to avoid turning off permission checking.) The fs(8) and kfscmd(8) manual pages explain more file system commands.
To create a new user, you can run
disk/kfscmd 'newuser tor'
it will automatically perform the following tasks
- add a line like
282:tor:tor:
to /adm/users
- run disk/kfscmd user - run the following commands
disk/kfscmd 'create /usr/tor tor tor 775 d'
I think these two commands have to be executed manually
disk/kfscmd 'create /mail/box/tor tor upas 775 d' disk/kfscmd 'create /mail/box/tor/mbox tor upas 622 al'
creating tor's home directory and mail box. Now you'll want to halt the disks and reboot to log in as tor; the first thing to do then is to set up a profile and start the window system by running
/sys/lib/newuser
Note that you had to reboot to log in as a different user; this is because the kernel must authenticate to the file server in order to obtain startup files like init or its startup script, and the only way for a terminal to get authentication credentials is to have a user type a name and password. Of course, for kfs this could be sidestepped, but this is necessary when booting from a real file server on the network.
When a Plan 9 machine boots, it runs the configuration script /rc/bin/termrc or /rc/bin/cpurc, depending on whether it is a terminal or a CPU server. These set up /dev and initialize some common environment variables, in particular $fileserver. This variable is used by lp, among other programs. For a standalone configuration, this should be kfs, as it is when installed; if you set up a real Plan 9 file server and boot over the network, change this to be the name of the network file server.
